Signal responsive device



May 24, 1955 R. PREssMAN SIGNAL RESPONSIVE DEVICE Filed Sept.e 27, 1952Fri/L INVENTOR.

RALPH-i PHESSMAN ATTORNEY United States Patent 0 SIGNAL RESPDNSIVEDEVICE Ralph Pressman, Philadelphia, Pa, assignor to Radio Corporationof America, a corporation of Delaware Application September 27, 1952,Serial N 311,842

17 Ciaims. (Cl. 367-458) This invention relates to a signal responsivedevice of the type known as a trigger or switching circuit in which theusual electron discharge tubes are replaced by a saturable core reactor.

In modern information handling apparatus such as digital computers,considerable utility is made of electronic switching and triggercircuits which are used to perform various control and storagefunctions. A basic form of such circuits is the Eccles-Jordan orflip-flop circuit which responds to input signals to produce twodifferent levels of output potential. The two outputs are produced bytwo different states of the circuit, which may be characterized by oneof the tubes of the circuit being either conductive or non-conductive.Generally, in the Eccles-Jordan type of circuit, two tubes are used; thetubes being cross-coupled so that a change in a tube to one stateproduces a change to the opposite state in the other tube. Thus, thecircuit has an essential binary character and mode of operation.

Due to the limited reliable life of an electron discharge tube leadingto problems of tube replacement, circuitry has been developed, in theart, which performs essentially the same function as electronic triggercircuits but which dispenses with the electron tube as the basic circuitelement. One such circuit is described in the Thompson Patent No.2,519,513. See also the Wood Patent No. 2,524,154. These circuits makeuse of a pair of saturable core reactors (magnetic cores each withalternating and direct current coils wound thereon) which arecross-coupled in a manner analogous to the archetype Eccles-Jordancircuit. These saturable core reactor circuits also have a binarycharacter or mode of operation. Two different levels of output potentialare produced by two different states of the circuit which may becharacterized by one of the magnetic cores being either saturated orunsaturated. As indicated in the above cited patents, trigger circuitsusing saturable core reactors may replace electron tube circuits in manyapplications.

The saturable core reactor trigger circuits of the prior art depend onone reactor being in a saturated state to maintain the other reactor inan unsaturated state. Similarly, a change in the state of saturation inone reactor is used to produce the opposite in the other reactor.Replacement of one of the two saturable reactors by a simple electriccircuit so as to produce substantially the same result would apparentlybe an economical simplification.

Accordingly, it is an object of this invention to provide a new signalresponsive device in which a saturable core reactor is used as a basiccircuit element.

Another object of this invention is to provide a signal responsivedevice having a binary mode of operation utilizing but a singlesaturable core reactor as a basic circuit element.

Still another object of this invention is to provide an economicalsignal responsive device utilizing a single saturable core reactor.

A feature of this invention is that a variation in permeability in areactor core produces a variation in the induc- 2,709,225 Fatented May24, 1955 tive coupling between two coils to produce a voltage forcontrolling core permeability.

These. and other objects of this invention are achieved by utilizing asingle saturable core reactor having a magnetic core and a biasing coilenergized from a unidirectional current source for varying thepermeability of the core between saturated and unsaturated conditions. Acontrol network is provided which includes the saturable core reactorand at least one inductance element. The network is energized byalternating current, and its inductive characteristics vary withvariations in core permeability. An output terminal of the controlnetwork is coupled to the biasing coil through a rectifier, knownhereafter as the biasing coil rectifier. With changes in corepermeability, output voltages are produced at the output terminal whichpermit or oppose flow of current in the biasing coil, and thus, controlthe permeability of the core. In the embodiment disclosed in detailbelow, the control network comprises a primary coil on the magnetic coreconnected to a source of alternating voltage, and a secondary coil onthe core inductively coupled to the primary coil through the magneticcore and connected through a rectifying circuit to the output terminal.

Changes in core permeability may be initiated by input signals appliedto an input terminal coupled to the biasing coil rectifier. An inputsignal voltage opposes the source voltage applied to the biasing coiland thus blocks flow of current in the biasing coil. The permeability ofthe core increases when the biasing current is removed, and theinductive coupling between the coils of the control network increases.As a result, there is an increase in voltage induced in the secondarycoil of the network. This voltage is rectified and applied to thebiasing coil rectifier to continue the blocking of current in thebiasing coil. The core remains in this state until another input signalof opposite polarity is received. This signal reduces the voltage at thebiasing coil rectifier and permits current flow in the biasing coil tosaturate the core. Saturation of the core reduces the coupling of thecoils in the network. Thus there is no voltage induced in the secondarycoil to oppose current flow in the biasing coil, and the core remains ina saturated state.

The organization and method of operation of the invention may be bestunderstood from the following description and the accompanying drawingin which there is shown a schematic circuit diagram of an embodiment ofthe invention.

Referring now to the drawing, there is shown a single saturable corereactor comprising a magnetic core 2 having three coils 4, 6, 8 thereon.One of the coils is a saturating or biasing coil 4, and it is energizedfrom the positive side of a source 10 of unidirectional voltage; theenergizing circuit being completed through a rectifier 12 and a loadresistor 14 to ground. Another coil 6 is connected to a source ofoscillating voltage 16 and functions as the primary coil of atransformer network which controls current flow in the biasing coil 4.The third coil 8, the secondary of the control network, is inductivelycoupled to the primary coil 6 through the magnetic core 2, and has itsends connected through a pair of rectifiers 18, 20 to an output terminal22. The load resistor 14 and a peaking condenser 24 are connectedbetween the output terminal 22 and a center tap 26 on the secondary coil8. The center tap of the secondary coil is connected to groundpotential. An input terminal 28 is coupled through a condenser 30 to thecathode 32 of the biasing coil rectifier 12, and it receives inputsignals from any appropriate source 34 of positive and negative pulses.The output terminal 22 is also connected to the cathode 32 of thebiasing coil rectifier 12.

The unidirectional current flowing through the biasing coil 4 is ofsufficient magnitude to saturate the magnetic core 2. When current isblocked in the biasing coil 4, the permeability of the magnetic core 2increases and the core is essentially in an unsaturated condition. Whenthe core is unsaturated, its permeability is high and, therefore, theinductive coupling through the core between the coils 6, 8 of thecontrol network is large. At that time, the oscillating flux produced bythe current in the primary coil 6 induces a voltage in the secondary 8.When the core is saturated, the inductive coupling through the corebetween the coils 6, S is reduced substantially, and any voltage inducedin the secondary coil 3 is insignificant.

Considering the condition when a unidirectional current is flowing inthe biasing coil 4, the magnetic core is saturated and voltage is notinduced in the secondary coil 8. The potential at the output terminal 22is above ground potential by the drop across the load resistor 14 causedby biasing coil current flowing therethrough. If a positive signal pulseis applied to the input terminal 23, the peaking condenser 24 chargesand the voltage at the cathode 32 of the biasing coil rectifier l2 risesto oppose the voltage applied to the biasing coil 4. The voltage rise atthe rectifier cathode 32 is sutficient to cut oil current flow in thebiasing coil. With the blocking of the saturating current, the couplingbetween the coils 6, 8 of the control network increases and a voltage isinduced in the secondary coil.

The res .lting current flow in the secondary coil ciicult is rectified,and the voltage drop across the load resistor 14 maintains a highvoltage at the output terminal 22. This control voltage is applied tothe cathode 32 of the biasing coil rectifier, and has a magnitudesufiicient to maintain or stabilize the blocking of current in thebiasing coil. The period of the oscillating voltage is small relative tothe time constant of the blocking circuit formed by the peakingcondenser 24 and the load resistor 14. As a result, rectification canbuild up a blocking voltage before the peaking condenser voltage decaysbelow the value necessary to block flow of. saturating current.

The circuit remains in this stable condition of the biasing currentblocked and the core saturated until a negative signal pulse is appliedto the input terminal 28. This pulse reduces the potential at thecathode 32 of the biasing coil rectifier l2 and initiates current fiovin the biasing coil 4. The core is again saturated and the couplingbetween the coils 6, 8 of the impedance network is substantiallyreduced. Thus, the voltage at the output terminal 22 continues to below, and current flow is maintained in the biasing coil until the nextpositive input pulse is received.

The output terminal 22 of the control network may be used as the outputterminal of the entire circuit. Two stable levels of potential areprovided at the output terminal as in the usual trigger circuit. Whenthe core is saturated, the potential at the output terminal is aboveground due to the voltage drop produced in the load resistor 14 by thebiasing coil current. When the core is unsaturated the terminal is muchmore above ground potential due to the rectified current from thesecondary coil being larger than the biasing coil current.

These output potentials may be used for switching or gating purposes inthe usual manner. Where the device to be controlled by the outputvoltages draws a significant amount of current, the voltage at theoutput terminal may be reduced below the level required for blockingcurrent in the biasing coil. Under such circumstances, an auxiliaryoutput circuit may be provided.

The auxiliary output circuit is identical to the secondary coil circuitpreviously described and comprises an additional coil 36 on the coreinductively coupled to the primary coil 6, a pair of rectifiers 38, 46connected to the ends of the coil 36, a center tap connected to ground,and a load resistor 44 and peaking condenser 46 connected between thecenter tap 42 and the cathodes of the rectifiers 38, 40. An outputterminal 48 is provided at the cathodes of rectifiers 38, 40 in the samemanner as previously described. This output terminal 48 presents twolevels of output potential, and small currents drawn from this circuitdo not materially affect the operation of the circuit.

The schematic circuit diagram is intended for explanatory purposes andnot to show actual construction of the core and windings since suitablearrangements are well known in the art. For example, a three-leggedmagnetic core may be used, with the primary coil wound on the outer legsand the biasing coil on the center leg to prevent induction ofoscillating voltages in the biasing coil.

It is, therefore, evident from the above description that a simplesignal responsive device is provided utilizing but a single saturablecore reactor which is economical in the components required.

What is claimed is:

1. A signal responsive device comprising a control network including (1)a saturable magnetic core, (2) a first coil on said core, and (3) meansfor applying an oscillatin voltage to said network, a biasing coil onsaid core, means for applying a unidirectional voltage to said biasingcoil, input means whereby a variation in core permeability may beproduced and thereby a variation in an electrical characteristic of saidcontrol network, and circuit means connecting said control network tosaid biasing coil for afiecting current flow in said biasing coil inaccordance with a variation in an electrical characteristic of saidcontrol network whereby variations in core permeability are controlled.

2. A signal responsive device as recited in claim 1 wherein said controlnetwork has an output terminal, variations in core permeabilityproducing variations in voltage at said output terminal, and saidcircuit means connects said output terminal to said biasing coil.

3. A signal responsive device as recited in claim 2 wherein said controlnetwork includes a secondary coil on said core inductively coupledthereby to said first coil, and rectifier means coupling said secondarycoil to said output terminal, variations in core permeability producingvariations in the inductive coupling between the first and secondarycoils of said network.

4. A signal responsive device as recited in claim 2 wherein said circuitmeans includes a rectifier connected between said output terminal andsaid biasing coil whereby current flow in said biasing coil depends onthe voltage at said output terminal.

5. A signal responsive device comprising a single saturable magneticcore, a coil on said core, means for applying an oscillating voltage tosaid coil, a biasing coil on said core, means for applying aunidirectional voltage to said biasing coil, input means wherebyvariations in the permeability of said core may be produced, and circuitmeans coupled to said oscillating voltage coil and to said biasing coilfor producing a unidirectional voltage having a direction opposite tothat of the voltage applied to said biasing coil responsive to avariation in the pernieability of said core.

6. A signal responsive device comprising a single sat urable magneticcore, a first circuit including (1) a coil on said core, and (2) meansfor applying an oscillating voltage to said coil, a biasing circuit forvarying the permeability of said core including (1) a second coil onsaid core, and (2) means for applying a unidirectional voltage to saidsecond coil, input means whereby a variation in core permeability may beproduced, and circuit means coupling said first circuit to said biasingcircuit for reflecting a variation in core permeability to said biasingcircuit whereby a variation in core permeability is stabilized.

7. A signal responsive device comprising a single saturable magneticcore, a first circuit including (1) a coil on said core, and (2) means:for applying an oscillating voltage to said coil, a biasing circuit forvarying the permeability of said core including (1) a biasing coil onsaid core, and (2) means for applying a unidirectional voltage to saidbiasing coil, an input terminal for receiving input signals, circuitmeans coupling said input terminal to said biasing circuit wherebycurrent flow in said biasing coil is changed upon reception of an inputsignal, and circuit means coupling said oscillating voltage circuit tosaid biasing circuit for reflecting a variation in core permeability tosaid biasing circuit whereby variations in core permeability arecontrolled.

8. A signal responsive device comprising a saturable magnetic core, acoil on said core, means for applying a source of oscillating voltage tosaid coil, a biasing circuit including a biasing coil on said core forreceiving a unidirectional current of saturation magnitude, an inputterminal for receiving an input signal, means coupling said inputterminal to said biasing circuit for applying an input signal to saidcircuit to block flow or" current in said biasing coil, and circuitmeans coupled to said oscillating voltage coil and effective uponcurrent flow being blocked in said biasing coil to apply a signal tosaid biasing circuit to maintain the blocking of said current flow.

9. A signal responsive device comprising a saturable magnetic core, afirst coil on said core, means for applying a unidirectional current tosaid coil to change the permeability of said core, an input terminal forreceiving input signals, means coupled to said input terminal and tosaid first coil for blocking flow of said unidirectional current uponapplication of a signal to said input terminal whereby the permeabilityof said core is changed, and scans including a second coil on said corefor maintaining the blocking of said unidirectional current responsiveto a change in the permeability of said core.

10. A signal responsive device comprising a control network including amagnetic core and an output terminal, a first coil on said core, meansfor applying a unidirectional current to said coil, input means wherebythe permeability of said core may be varied, and a rectifier having afirst and a second electrode, said first rectifier electrode beingconnected to said first coil, said network output terminal beingconnected to said second rectifier electrode, said control networkincluding a second coil on said core and being responsive to an increasein the permeability of said core for producing a voltage at said outputterminal to oppose flow of current in said first coil and responsive toa decrease in the permeability of said core for producing a voltage atsaid output terminal to permit flow of current in said first coil.

11. A signal responsive device comprising a saturable magnetic core, aprimary coil on said core, means for applying an oscillating voltage tosaid primary coil, a secondary coil on said core inductively coupled tosaid primary coil, means for determining the permeability of said coreand thereby determining the inductive coupling between said primary andsecondary coils, and means coupling said secondary coil to saidpermeability determining means for stabilizing the determinedpermeability of said core.

12. A signal responsive device comprising a saturable magnetic core, afirst winding, means to apply an exciting current to said first winding,a second winding coupled to said first winding through said core, meansto saturate said core whereby the coupling between said first and secondwinding is rendered inedectual, means to apply an inactivating signal tosaid core saturating means, and means coupling said second Winding tosaid core saturating means to maintain said core saturating meansinactivated following the application of said inactivating signal.

i5 13. A signal responsive device comprising a control retworl;including (1) a saturable magnetic core, (2) a -y coil on said core, (3)means for applying an c inductively coupled thereby to said primary (.5;an output terminary, (6) rectifier means cou ling said secondary coil tosaid output terminal, a biasing coil on s id core, means for applying aunidirectional voitage said biasing coil to produce biasing currenttherein, input means whereby the permeability of i re is varied, and abiasing coil rectifier element coupling said output terminal to saidbiasing coil whereby a variation in core permeability produces avariation in voltage at said output terminal and thereby at saidrectifier element to control current flow in said biasing coil.

14. A signal responsive device as recited in claim 13 wherein said inputmeans includes an input terminal coupled to said biasing coil rectifierelement whereby an input signal may be applied to said input terminal tovary the vol e at said rectifier element.

l responsive device as recited in claim 14 wherein said rectifier meansincludes a second and third rectifier element each having a pair ofelectrodes, one electrode of each of said second and third rectifierelements being connected to difierent ends of said secondary coil, and aresistor and a capacitor connected in parallel between the others ofsaid rectifier electrodes and a central point on said secondary coil,said output terminal being connected to the others of said rectifierelectrodes, and said biasing coil rectifier includes a pair ofelectrodes, one of said biasing coil rectifier electrodes beingconnected one end of said biasing coil, and the other of said biasingcoil rectifier electrodes being coupled to said input and outputterminals.

16. A signal responsive device comprising a saturable magnetic core, aprimary coil on said core, means for applying an oscillating voltage tosaid first coil, two secondary coils on said core each inductivelycoupled to said pri'nary coil, two output terminals, separate rectifiermeans coupling each of said secondary coils to a different one of saidoutput terminals, a biasing coil on said core, means for applying aunidirectional voltage to said biasing coil, an input terminal, and arectifier element coupling said input terminal and one of said outputterminals to said biasing coil.

l7. A signal responsive circuit having two stable states comprising asingle magnetic core, a biasing circuit including a biasing coil on saidcore for receiving a unidirectional current of predetermined magnitude,said core having one and another permeability respectively when saidunidirectional current is flowing and not flowing in said biasing coil,and circuit means responsive to the state of permeability of said corefor controlling the flow of said unidirectional current, whereby saidsignal responsive circuit is in one or the other of said stable statesaccordingly as said unidirectional current is flowing or not flowing.

References Cited in the file of this patent Publication, An ElectronicDigital Computer, by A. D. Booth, in Electronic Engineering (British),December 1950, pages 492498.

Publication, Static Magnetic Storage and Delay Line, by An Wang and WayDong Woo; Journal of Applied Physics, January 1950 (paper received July27, 1949), Pages 49-54.

Publication, Progress Report (2) on the Edvac, vol. II, published June30, 1946, Moore School of Electrical Engineering, U. of Pa.,Philadelphia, Pa., especially paragraph 4.2.12, etc., and Figs. 17a, b,and c.

